Arduino Nano support - Error while connecting to device

[GChalony]

I've just gotten an Arduino Nano Esp32, and would like to get started with Rust Embedded.
However, it seems espflash cannot communicate with it:

$ espflash board-info
[2025-11-11T18:45:06Z INFO ] Serial port: '/dev/ttyACM0'
[2025-11-11T18:45:06Z INFO ] Connecting...
Error:   × Failed to open serial port /dev/ttyACM0
  ╰─▶ Error while connecting to device

I have followed the instructions regarding the Linux permissions, and added the udev rules with an obscure script.
I can flash through the Arduino IDE, and have access to the Serial Monitor.

I have read #534 and tried to short B1 and ground, but the error is still the same.

Sorry I'm just getting started so this might be very simple, but is there any thing to do to be able to flash ?

[bugadani]

Failed to open serial port /dev/ttyACM0

This is a bit suspicious, but let's start with the easy bits:

Although you said you've shorted the B1 pin to ground, here's the complete process for clarity:

• Press and hold the reset button (or unplug the Arduino).
• Short the B1 pin (GPIO0) to GND.
• Release the reset button (or connect the arduino to your PC), while GPIO0 is still shorted.
• You can now remove the short from GPIO0.
• At this point espflash should be able to connect to the device.

This method should work because USB is wired directly into the ESP32-S3 chip, and unless Arduino or ublox modified the default chip eFuses, the chip should provide a CDC-ACM and a custom JTAG interface on its USB port.

A few things to note: the device must not be kept in reset while you're trying to connect to it. The B1 pin is sampled when the reset pin is de-asserted (or when the device powers on), so you only really need to short it for a short time. The B1 pin will keep your device in "Download mode", you will need another reset to bring the chip out of it to boot normally. espflash should also be able to connect even without Download mode, once you get rid of the arduino bootloader.

[GChalony]

Thanks for the detailed info. I've tried to follow the steps precisely, but with the same result.
The LED turns green when B1 is shorted, then purple when removed (after I released the reset).

I've tried switching USB cable with the same result.
A few more tests:

$ esptool --port /dev/ttyACM0 chip-id
esptool v5.1.0
Serial port /dev/ttyACM0:

A fatal error occurred: Could not open /dev/ttyACM0, the port is busy or doesn't exist.
([Errno 16] could not open port /dev/ttyACM0: [Errno 16] Device or resource busy: '/dev/ttyACM0')

$ espflash --version
espflash 4.2.0

$ ls -lah /dev/ttyACM0
crw-rw-rw-. 1 root dialout 166, 0 Nov 11 20:58 /dev/ttyACM0

$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 034: ID 0a5c:5834 Broadcom Corp. 5880
Bus 001 Device 050: ID 2341:0070 Arduino SA Nano ESP32
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 004: ID 413c:81b6 Dell Computer Corp. DW5811e Snapdragon™ X7 LTE

$ hostnamectl                                                                                                                                          in nu at 21:01:27
     Static hostname: gregnix-laptop
           Icon name: computer-laptop
             Chassis: laptop 💻
          Machine ID: 1d8a5b028e034a22818311d939b26ccb
             Boot ID: fa2021f54abf4eefa7ffe35b5373f76c
    Operating System: Fedora Linux 43 (Workstation Edition)
         CPE OS Name: cpe:/o:fedoraproject:fedora:43
      OS Support End: Wed 2026-12-02
OS Support Remaining: 1y 2w 5d                             
              Kernel: Linux 6.17.6-300.fc43.x86_64
        Architecture: x86-64
     Hardware Vendor: Dell Inc.
      Hardware Model: Latitude 7480
        Hardware SKU: 07A0
    Hardware Version: A00
    Firmware Version: 1.40.0
       Firmware Date: Tue 2024-11-05
        Firmware Age: 1y 6d

[bugadani]

I find it weird that the device identifies itself as Bus 001 Device 050: ID 2341:0070 Arduino SA Nano ESP32. For that to happen, software needs to run, and that is not what should be happening in download mode. Did you run lsusb while the boot pin was still shorted, or without it?

[GChalony]

I wasn't sure so I tried both:

Without B1 shorted
Bus 001 Device 053: ID 2341:0070 Arduino SA Nano ESP32

With B1 shorted
Bus 001 Device 054: ID 303a:1001 Espressif USB JTAG/serial debug unit

[bugadani]

All right, it looks like you're correctly using the B1 pin to trigger Download mode. In this mode espflash should just work, if it doesn't, then you may have some OS-specific setup problem that I don't think I can help you with. I'm guessing the udev rules you installed don't contain Espressif-specific IDs. You can use the relevant bits of the probe-rs documentation - there is a udev rules file there, which contains Espressif identifiers. But as I have relatively little Linux experience, I don't know if this is the root of your problem.

[GChalony]

Well it turns out that I just needed to reload the udev rules, a pointed out in the probe-rs docs 😅

[2025-11-13T22:26:41Z INFO ] Serial port: '/dev/ttyACM0'
[2025-11-13T22:26:41Z INFO ] Connecting...
[2025-11-13T22:26:41Z INFO ] Using flash stub
Chip type:         esp32s3 (revision v0.1)
Crystal frequency: 40 MHz
Flash size:        16MB
Features:          WiFi, BLE, Embedded Flash
MAC address:       34:85:18:7b:06:08

Security Information:
=====================
Flags: 0x00000000 (0)
Key Purposes: [0, 0, 0, 0, 0, 0, 12]
Chip ID: 9
API Version: 0
Secure Boot: Disabled
Flash Encryption: Disabled
SPI Boot Crypt Count (SPI_BOOT_CRYPT_CNT): 0x0

Thanks for all your help, you've been super quick :D